Underscore.js 是一个 JavaScript 工具库，它提供了一整套函数式编程的实用功能，但是没有扩展任何 JavaScript 内置对象。Underscore 提供了100多个函数，包括常用的：map、filter、invoke — 当然还有更多专业的辅助函数，如：函数绑定、JavaScript 模板功能、创建快速索引、强类型相等测试等等。 微信小程序无法直接使用require( 'underscore.js' )进行调用。
微信小程序模块化机制
微信小程序运行环境支持CommoJS模块化，通过module.exports暴露对象，通过require来获取对象。
微信小程序Quick Start utils/util.js
function formatTime(date) {
var year = date.getFullYear()
var month = date.getMonth() + 1
var day = date.getDate()
var hour = date.getHours()
var minute = date.getMinutes()
var second = date.getSeconds();
return [year, month, day].map(formatNumber).join('/') + ' ' + [hour, minute, second].map(formatNumber).join(':')
}
function formatNumber(n) {
n = n.toString()
return n[1] ? n : '0' + n
}
module.exports = {
formatTime: formatTime
}
pages/log/log.js
var util = require('../../utils/util.js')
Page({
data: {
logs: []
},
onLoad: function () {
this.setData({
logs: (wx.getStorageSync('logs') || []).map(function (log) {
return util.formatTime(new Date(log))
})
})
}
})
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原因分析
Underscore CommonJs模块导出代码如下：
// Export the Underscore object for **Node.js**, with
// backwards-compatibility for the old `require()` API. If we're in
// the browser, add `_` as a global object.
if (typeof exports !== 'undefined') {
if (typeof module !== 'undefined' && module.exports) {
exports = module.exports = _;
}
exports._ = _;
} else {
root._ = _;
}
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exports、module必须都有定义，才能导出。通过测试，微信小程序运行环境exports、module并没有定义
//index.js
//获取应用实例
var app = getApp();
Page({
onLoad: function () {
console.log('onLoad');
var that = this;
console.log('typeof exports: ' + typeof exports);
console.log('typeof module: ' + typeof exports);
var MyClass = function() {
}
module.exports = MyClass;
console.log('typeof module.exports: ' + typeof module.exports);
}
})
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解决方法
修改Underscore代码，注释原有模块导出语句，使用module.exports = _ 强制导出
/*
// Export the Underscore object for **Node.js**, with
// backwards-compatibility for the old `require()` API. If we're in
// the browser, add `_` as a global object.
if (typeof exports !== 'undefined') {
if (typeof module !== 'undefined' && module.exports) {
exports = module.exports = _;
}
exports._ = _;
} else {
root._ = _;
}
*/
module.exports = _;
/*
// AMD registration happens at the end for compatibility with AMD loaders
// that may not enforce next-turn semantics on modules. Even though general
// practice for AMD registration is to be anonymous, underscore registers
// as a named module because, like jQuery, it is a base library that is
// popular enough to be bundled in a third party lib, but not be part of
// an AMD load request. Those cases could generate an error when an
// anonymous define() is called outside of a loader request.
if (typeof define === 'function' && define.amd) {
define('underscore', [], function() {
return _;
});
}
*/
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使用Underscore.js
//index.js
var _ = require( '../../libs/underscore/underscore.modified.js' );
//获取应用实例
var app = getApp();
Page( {
onLoad: function() {
//console.log('onLoad');
var that = this;
var lines = [];
lines.push( "_.map([1, 2, 3], function(num){ return num * 3; });" );
lines.push( _.map( [ 1, 2, 3 ], function( num ) { return num * 3; }) );
lines.push( "var sum = _.reduce([1, 2, 3], function(memo, num){ return memo + num; }, 0);" );
lines.push( _.reduce( [ 1, 2, 3 ], function( memo, num ) { return memo + num; }, 0 ) );
lines.push( "var even = _.find([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });" );
lines.push( _.find( [ 1, 2, 3, 4, 5, 6 ], function( num ) { return num % 2 == 0; }) );
lines.push( "_.sortBy([1, 2, 3, 4, 5, 6], function(num){ return Math.sin(num); });" );
lines.push( _.sortBy( [ 1, 2, 3, 4, 5, 6 ], function( num ) { return Math.sin( num ); }) );
lines.push( "_.indexOf([1, 2, 3], 2);" );
lines.push( _.indexOf([1, 2, 3], 2) );
this.setData( {
text: lines.join( 'n' )
})
}
})
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